1. Technical Field
The present invention relates generally to motor vehicle drive trains and more particularly to an axle assembly wherein the axle vent is mounted to a carrier housing.
2. Discussion
Axle assemblies are typically partially filled with a lubricating fluid to lubricate various gears, pinions and bearings during the operation of a vehicle. Under normal operating conditions, the temperature of the fluids in the axle assembly (i.e., the lubricating fluid and air) increase, causing the fluids to expand. The fluids subsequently cool and contract after the vehicle is maintained in an inoperative state for a period of time. Generally, axe assemblies are equipped with a vent connector that is mounted directly to the carrier housing or the axle housing to permit air to exit and enter the axle assembly when the fluids contained therein expand and contract. While this solution has been generally effective in its employment, several drawbacks have been noted.
One such drawback concerns a situation wherein a leak occurs at the intersection between the carrier or axle housing and the vent. Leaks may occur as a result of porosity in the cast housing or an improperly machined hole into which the vent is press-fit or threadably engaged. Often times the leak is small and not readily noticeable. In such situations it is possible for water to pass into the housing and intermingle with the lubricating fluid to thereby reduce its effectiveness. If the leak is detected, it is relatively common to scrap the housing. As the housings are machined from castings which are typically expensive and as the housings are typically fully machined at the point when the leak is detected, the scraping of a housing is expensive.
Anther drawbacks concern the difficulty of machining the hole for the vent into the housing. Typically these holes are formed in a contoured area of the housing which can cause difficulties in the hole forming process. Twist drills typically wander from their intended target position when they are employed to drill a hole on a curved surface. Drills which wander typically drill an oval-shaped and oversized hole in the housing, which increases the risk that the intersection between the housing and the vent will leak. Furthermore, wandering greatly reduces the life of the twist drill and the drill bushings.
Accordingly, there remains a need in the art for an axle assembly which may be vented in a cost-effective manner without forming a hole in the carrier housing or axle housing.
In one form, the present invention provides an axle assembly having a carrier housing, an axle housing and a differential assembly and a cover assembly. The carrier housing has an access aperture for receiving the differential assembly. The axle housing is fixedly coupled to the carrier housing and is in fluid connection therewith. The cover assembly closes the access aperture and includes a venting device for venting the carrier housing and the axle housing.